1. Field of the Invention
The present invention relates to integrated circuits and, more in particular, to analog integrated circuits.
2. Discussion of the Prior Art
The fundamental parameters which determine the intrinsic characteristics of an analog circuit are, in large measure, determined by the intrinsic structural characteristics of particularly significant circuit components. Therefore in designing analog integrated circuits it is necessary to properly and systematically size dimensions and other structural characteristics of circuit components. A typical example is represented by the operational amplifier (truly a building block of a large number of analog circuits), which at present is made in accordance with set specifications. A customer is therefore bound to change type of integrated operational amplifier depending upon the application, as well as a semiconductor device manufacturer is obliged to re-design the operational amplifier for particular applications and therefore to change the masks used in the fabrication in order to satisfy the required specifications. The only solution known to allow a certain degree of alterability of the intrinsic characteristics of an integrated operational amplifier is to modify by external means the bias current level of the amplifier through a dedicated input pin of the integrated device. The variations of the amplifier's performances obtainable by this technique are substantially limited only to few parameters (typically the gain and the power conception) while it is difficult for example to substantially modify the pass-band width and moreover the variations which may be obtained are confined within a rather narrow range about a nominal value.